1. Field of the Invention
The present invention relates to a sheet processing method of performing a predetermined process on sheets, a sheet processing apparatus for implementing the sheet processing method, and an image forming apparatus having the sheet processing apparatus.
2. Description of Related Art
Heretofore, some image forming apparatuses, such as printers, are provided with a sheet processing apparatus for aligning a plurality of sheets having images formed (printed) thereon and, then, performing a process on the sheets, such as stapling (driving needles into) the end parts of the sheets.
Such a sheet processing apparatus is, in many cases, provided as an option unit which is detachably attached to a printer or a copying machine, and is mounted in such a way as to be connected directly with a sheet discharge port of the body of the image forming apparatus. Then, sheets which have been subjected to printing at the image forming apparatus body are sequentially supplied from the sheet discharge port to the sheet processing apparatus, at which the sheets are aligned and are, then, subjected to a predetermined process.
However, in such a conventional image forming apparatus, there are such inconveniences that, in order to discharge and stack, in the order of page numbers, the sheets subjected to printing at the image forming apparatus body, it is necessary to provide the sheet processing apparatus with an inverting mechanism for inverting sheets, or it is necessary to assure a wide interval between the sheets so as to allow an inverting action on the sheets.
Further, since the sheet processing apparatus is disposed at the side of the sheet discharge port of the image forming apparatus body, not only the area of installation of the whole image forming apparatus is caused to increase, but also the production cost of the image forming apparatus is caused to rise disadvantageously.